The present invention relates to a method and a device, respectively, for providing traction control of a motor vehicle.
In German Published Patent Application No. 35 45 716 is discussed a device for propulsion control of motor vehicles, in which, for the purpose of preventing undesired spinning of driven vehicle wheels (slip) they are braked, or rather their drive torque is reduced, when a predefined threshold value of slip (slip threshold) is exceeded. For this purpose, a plurality of slip thresholds are predefined which take effect as a function of transverse acceleration and vehicle speed. Thus, for example, the transverse acceleration is measured by a cornering recognition device, and from this a value is derived for the reduction of the initial drive torque if only one wheel spins, and there is either low transverse acceleration and high vehicle speed or high transverse acceleration and low vehicle speed.
Conditional upon the definitively predefined slip thresholds, it may be that, to a great extent, traction control can be performed, but adjusting and optimizing for the actual curve shape of the road may only be possible to some extent.
An exemplary method and/or exemplary embodiment according to the present invention is believed to have the advantage that the threshold value for slip in the transverse direction to the vehicle is determined as a function of the radius of curve of the road. During cornering, the drive axle wheel on the inside of the curve is unloaded comparatively greatly, so that it has a greater slip value than the wheel on the outside of the curve. Definitively predefined thresholds here may have the disadvantage that the wheel on the inside of the curve reaches the definitively predefined slip threshold earlier than desired than the wheel at the outside of the curve. Of necessity this may then have the result that the drive torque is reduced too early, in spite of the fact that this wheel with regard to its slip is not critical as to safety. It is therefore considered an advantage not to predefine the slip threshold definitively but adapted to the shape of the road as a function of the radius of curve.
It is also believed to be advantageous that, in addition to the slip threshold, the transverse acceleration of the vehicle, possibly that of the xe2x80x9cmiddle axlexe2x80x9d, is considered, since the transverse acceleration, besides the radius of curve, also represents a measure of traction reserve.
By the additional measurement of the travel speed, it is believed that the slip value may be advantageously determined in a simple way for individual wheels, without great effort.
It is also believed to be advantageous that the slip threshold is determined as a function of the curve direction, because this allows the assignment of the transverse acceleration to the corresponding wheel on the inside of the curve.
It is also believed to be advantageous that the control system determines a weighting factor for ascertaining the slip. Thereby street conditions, such as country roads of different categories or expressways having different properties with respect to drivability can be better considered.
The dependence of the weighting factor as a straight line function may be provided using a software program, and should not require major storage.
By increasing the slip threshold for the wheel on the inside of the curve which is engine-driven, higher travel speeds should result without the vehicle""s becoming unstable or reaching a condition critical as to safety. Weighting, using the weighting factor, here represents a way of adapting the slip threshold linearly to the radius of curve.
Since in sustained curves having a very large radius of curve the risk of a risky driving maneuver may be relatively low, it may be sufficient to limit the slip threshold to a minimum value.